Known as a conventional spectroscopic sensor is one comprising a plurality of interference filter units for transmitting therethrough light having a predetermined wavelength according to an incident position of the light, a light-transmitting substrate for transmitting therethrough the light incident on the interference filter units, and a light detection substrate for detecting the light transmitted through the interference filter units. There is a case where each interference filter unit is constructed as that of Fabry-Perot type by making a pair of mirror layers oppose each other through a cavity layer (see, for example, Patent Literature 1).